import { isClient } from '@vueuse/core'
import { getStyle } from './style'

export function isScroll(el: HTMLElement, isVertical?: boolean): boolean {
  if (!isClient)
    return false

  const key = (
    {
      undefined: 'overflow',
      true: 'overflow-y',
      false: 'overflow-x',
    } as const
  )[String(isVertical)]!
  const overflow = getStyle(el, key)
  return ['scroll', 'auto', 'overlay'].some(s => overflow.includes(s))
}

export function getScrollContainer(el: HTMLElement, isVertical?: boolean): Window | HTMLElement | undefined {
  if (!isClient)
    return

  let parent: HTMLElement = el
  while (parent) {
    if ([window, document, document.documentElement].includes(parent))
      return window

    if (isScroll(parent, isVertical))
      return parent

    parent = parent.parentNode as HTMLElement
  }

  return parent
}

let scrollBarWidth: number
export function getScrollBarWidth(): number {
  if (!isClient)
    return 0
  if (scrollBarWidth !== undefined)
    return scrollBarWidth

  const outer = document.createElement('div')
  // Cannot access 'propKey' before initialization
  // need to be dynamic namespace
  outer.className = 'el-scrollbar__wrap'
  outer.style.visibility = 'hidden'
  outer.style.width = '100px'
  outer.style.position = 'absolute'
  outer.style.top = '-9999px'
  document.body.appendChild(outer)

  const widthNoScroll = outer.offsetWidth
  outer.style.overflow = 'scroll'

  const inner = document.createElement('div')
  inner.style.width = '100%'
  outer.appendChild(inner)

  const widthWithScroll = inner.offsetWidth
  outer.parentNode?.removeChild(outer)
  scrollBarWidth = widthNoScroll - widthWithScroll

  return scrollBarWidth
}

/**
 * Scroll with in the container element, positioning the **selected** element at the top
 * of the container
 */
export function scrollIntoView(container: HTMLElement, selected: HTMLElement): void {
  if (!isClient)
    return

  if (!selected) {
    container.scrollTop = 0
    return
  }

  const offsetParents: HTMLElement[] = []
  let pointer = selected.offsetParent
  while (pointer !== null && container !== pointer && container.contains(pointer)) {
    offsetParents.push(pointer as HTMLElement)
    pointer = (pointer as HTMLElement).offsetParent
  }
  const top = selected.offsetTop + offsetParents.reduce((prev, curr) => prev + curr.offsetTop, 0)
  const bottom = top + selected.offsetHeight
  const viewRectTop = container.scrollTop
  const viewRectBottom = viewRectTop + container.clientHeight

  if (top < viewRectTop)
    container.scrollTop = top
  else if (bottom > viewRectBottom)
    container.scrollTop = bottom - container.clientHeight
}
